Hydrophobic test strip for analyzing whole blood



United States Patent 3,418,083 HYDROPHOBIC TEST STRIP FOR ANALYZING WHOLE BLOOD Hans-Georg Rey, Mannheim, and Peter Rieckmann, Mannheim-Waldhof, Germany, assignors to C. F. Boehringer & Soehne G.m.b.H., Mannheim-Waldhof, Germany No Drawing. Filed Mar. 17, 1966, Ser. No. 535,010 Claims priority, application Germany, May 20, 1965, B 82,023 8 Claims. (Cl. 23-253) This invention relates to a diagnostic agent for the detection of biochemical and chemical components in whole blood and more particularly relates to a test strip for use in the detection of chemical and biochemical components in whole blood, a process for the preparation of such test strips and a method for using the same.

The detection of biochemical and chemical components in whole blood has hirtherto been a very laborious, expensive and time-consuming procedure which can only be carried out in suitably equipped laboratories and with skilled personnel. The whole blood must first be processed to the serum or plasma in which only then can be analyzed for the substances of interest. Whole blood is not suitable as the strong coloring properties of hemoglobin would interfere or render inaccurate all color reactions.

Recently, procedures have been described which make possible the detection of glucose or urea in whole blood (of. US. Patent No. 3,092,465 and British Patent No. 922,665). The principle of these new procedures involves the covering of a test paper strip on the outside thereof with a semipermeable wall (made from various cellulose derivatives). When whole blood is placed on a strip of this type, the blood fluid, together with the components dissolved therein, passes through the semi-permeable film giving rise to a color reaction in the test paper, the red blood corpuscles remaining behind on the film. After a predetermined period of time, the blood coagulum (red cells) must be washed off in order that the color reaction developed in the underlying paper can be seen.

It is an object of the present invention to provide a new and improved test paper strip for use in detecting chemical and biochemical components of whole blood.

A further object of the invention is to provide a new and improved test paper strip for use in detecting chemical and biochemical components of whole blood characterized by the extreme ease with which they are produced and used.

These and other objects and advantages will be apparent from a consideration of the following disclosure.

In accordance with the invention, it has now been found that diagnostic agents for the detection of biochemical and chemical components in whole blood which are outstandingly useful and can be prepared in a substantially simpler and more economic manner than possible heretofore, are obtained by impregnating an absorbent carrier (preferably filter paper) impregnated with specific reagents and indicators which absorbent carrier is prior to, during, or following the impregnation hydrophobed. This result is completely surprising. It was not to have been foreseen that a hydrophobed absorbent carrier such as hydrophobed filter paper would be moistened with serum or plasma to such an extent that the reaction can take place in the filter paper While the red blood corpuscles are prevented, by the hydrophobing, from penetrating into 3,418,083 Patented Dec. 24, 1968 the paper so that they can be completely rinsed ofi' or wiped off with gauze, cloth, wadding or by cotton wool. In the case of non-hydrophobed test paper strips, the red blood corpuscles penerate so deeply into the filter paper that they can be neither wiped off nor rinsed out. However, due to their intense inherent color, they interfere with the actual color reactions to such an extent that the color change can no longer be observed or appreciated.

Exemplary instances of agents which can be used for the hydrophobing of the absorbent carriers are natural and synthetic fats, oils and waxes, as well as, and preferably, paraflins, silicones and mixtures thereof. Generally,

the conventional test paper strips can be hydrophobed following impregnation with the indicator solutions. However, dependable and satisfactory test paper strips are also obtained when the indicator dyestuff, together with the hydrophobing agent, is employed as impregnant being applied onto test paper strips which have already been impregnated with the other reagents.

For the production of the hydrophobed diagnostic agents according to the present invention, there can be used not only filter paper, but also other absorbent carriers, such as asbestos paper and Wood rodlets. However, the pores of the wood can sometimes be disturbing since red blood corpuscles collect therein and can only be wiped off or rinsed out with difficulty.

The diagnostic agents according to the present invention can be utilized for all of the clinical tests which are of importance in the analysis of blood, especially for the clinical screening tests, as for example, the determination of glucose, galactose, phenyl-alanine, serum cholinesterase, urea and uric acid, as well as for phosphatases, transaminases, dehydrogenases, trypsin, histidine, and the like.

Furthermore, an important advantage of the hydrophobed diagnostic agents according to the invention, in comparison with all diagnostic agents which have previously been suggested or used for the investigation of whole blood, is the extreme ease with which they are produced and used since sensitive and expensive special coatings or sealings are not necessary.

The following examples are given for the purpose of illustrating the present invention and are not to be construed as a limitation thereof.

EXAMPLE 1 Production of a test strip suitable for the detection of glucose in whole blood.

impregnation solution I Grams Peroxidase 0.012 Glucose oxidase 1.300 Primary potassium phosphate 0.269 Secondary sodium phosphate 0.004 Glycocoll 6.000 Distilled water ad 100.0 ml.

Impregnation solution II Grams o-Tolidine 0.420 Paraffin 4.000

Methylene chloride ad 100.0 ml.

Schleicher and Schiill filter paper No. 2312 was successively impregnated with impregnation solutions I and II, dried and cut up into strips of mm. width.

When a strip thereby obtained was moistened with a drop of blood, taken, for example, from a finger or ear lobe, the blood left to act upon the strip for 1 minute and the blood then rinsed off with water, there resulted a blue color reaction which was dependent upon the glucose content of the blood and which could be evaluated by reference to a comparative color scale. The same results were obtained when the methylene chloride was replaced by petrol ether.

EXAMPLE 2 Production of a test strip suitable for the detection of galactose in whole blood.

Impregnation solution I Methylene chloride ad 100.0 ml.

Schleicher and Schiill filter paper No. 2312 was successively impregnated with impregnation solutions -I and II, dried and cut up into strips. Blood containing galactose obtained as described above was applied to the test strips in a manner analogous to that described in Example 1 and the strips further processed as therein set forth. The test strips evidence the galactose content of the blood by a blue color reaction, the intensity of which is directly related to the amount of galactose present.

EXAMPLE 3 In place of the impregnation solution II used in Example 1, there was used a solution having the following composition:

Grams o-Tolidine 0.420 Silicone impregnation agent 2.000

Methylene chloride ad 100.0 m1.

Apart from this difference, the test strip was produced in exactly the same way as described in Example 1. The test strips thereby obtained had the same properties as those of Example 1 and produced the same results.

EXAMPLE 4 Phenyl-alanine test paper Filter paper was impregnated with L-amino acid oxidase, peroxidase and o-tolidine, together with a 0.2 molar phosphate buffer having a pH of 6.5. The dried paper was subsequently impregnated with a solution of 4% paraflin in methylene chloride. The phenyl-alanine test paper obtained in this manner demonstrated, upon the application thereto of blood, containing phenylalanine in a manner analogous to that described in Example 1, the content of L-phenyl-alanine by a blue color reaction which could be quantitatively evaluated by reference to a color table.

The same results were obtained when the paraffin was replaced by 2% silicone.

We claim:

1. A diagonstic agent for use in the detection of chemical and biochemical components in whole blood comprising an absorbent carrier support impregnated with a composition forming color in response to said chemical component and treated with a hydrophobing agent rendering the impregnated absorbent carrier hydrophobic, wherein said hydrophobing agent is a member selected from the group consisting of natural and synthetic fats, oils, waxes, parafiins, silicones, and mixtures thereof.

2. A diagnostic agent according to claim 1, wherein said absorbent carrier support is a member selected from the group consisting of filter paper, asbestos paper, and wood rodlets.

3. A diagonstic test agent according to claim 1, wherein said absorbent carrier support is impregnated with the following composition for forming color in response to said chemical component:

Grams Peroxidase 0.012 Glucose oxidase 1.300 Primary potassium phosphate 0.269 Secondary sodium phosphate 0.004 Glycocoll 6.000

Distilled water ad 100.0 ml. and is hydrophobed with the following composition:

Grams o-Tolidine 0.420 Parafiin 4.000

Methylene chloride ad 100.0 ml.

4. A diagnostic test agent according to claim 1, wherein said absorbent carrier support is impregnated with the following composition for forming color in response to said chemical component:

Grams Peroxidase 0.012 Galactose oxidase 0.300 Primary potasium phosphate 0.746 Secondary sodium phosphate 2.585

Distilled water ad 100.0 ml. and is hydrophobed with the following composition:

Grams o-Tolidine 0.420 Parafiin 4.000

Methylene chloride ad 100.0 ml.

5. A diagnostic test agent according to claim 1, wherein said absorbent carrier support is impregnated with the following composition for forming color in response to said chemical component:

Grams Peroxidase 0.012 Glucose oxidase 1.300 Primary potassium phosphate 0.269 Secondary sodium phosphate 0.004 Glycocoll 6.000

Distilled water ad 100.0 ml.

and is hydrophobed with the following composition:

Grams o-Tolidine 0.420 Silicone impregnation agent 2.000

Methylene chloride ad 100.0 ml.

6. The method of providing diagnostic agents for use in the detection of chemical and biochemical components in whole blood comprising impregnating an absorbent carrier support with a composition forming color in response to said chemical component and thereafter treating said impregnated carrier support with a hydrophobic agent rendering the impregnated carrier support hydrophobic, wherein said hydrophobic agent is a member selected from the group consisting of natural and synthetic fats, oils, waxes, paraffins, silicones and mixtures thereof.

7. Method according to claim 6, wherein said composition for forming color in response to said chemical component comprises a mixture of specific reagents and indicators.

8. Method according to claim 6, wherein said composition for forming color in response to said chemical component comprises a mixture of specific reagents and indicators and wherein said absorbent carrier is first 3,418,083 5 6 impregnated with said specific reagents and thereafter MORRIS O. WOLK, Primary Examiner. treated with the indicator and hydrophobing agent.

E. A. KATZ, Assistant Examiner. References Cited UNITED STATES PATENTS 5 US. Cl. X.R.

3,092,465 6/1963 Adams et a1. 3,298,789 1/1967 Mast 252408, 195-4035, 167-845 

1. A DIAGONSTIC AGENT FOR USE IN THE DETECTION OF CHEMICAL AND BIOCHEMICAL COMPONENTS IN WHOLE BLOOD COMPRISING AN ABOSRBENT CARRIER SUPPORT IMPREGNATED WITH A COMPOSTION FORMING COLOR IN RESPONSE TO SAID CHEMICAL COMPONENT AND TREATED WITH A HYDROPHOBING AGENT RENDERING THE IMPREGNATED ABSORBENT AGENT IS A MEMBER SELECTED FROM THE GROUP CONSISTING OF NATURAL AND SYNTEHTIC FATS, OILS, WAXES, PARAFFFINS, SILICONES, AND MIXTURES THEREOF. 